The technical development of ontology based systems has been a topic of interest for computing scientists since the early 1990s. Over the years a number different ontology formalisms, methodologies and their supporting tools have emerged to help subject specialists build ontologies. However when attempting to create an ontology of a wide ranging subject such as history a number of specific challenges related to the nature of the domain arise. These include time dependence, subjectivity and uncertainty. This paper illustrates the challenges from the ontological engineerss point of view which were encountered in the development of an ontology of European history during the recently completed VICODI project. Solutions to those challenges are suggested based on our experiences during this project. These include the application of a fuzzy sets based temporal model and the introduction of intermediate models above the ontology implementation level.